In general, the optical can include additional contributions from
reprocessed emission from hard X-ray illumination of the outer disc,
as well as contributions from the jet and the companion
star(e.g. [1]}). However, SWIFT J1753.5-0127 is a
short period, low mass X-ray binary, so the companion star must
faint. Instead we try to quantify the jet contribution from observed
radio flux of \(\sim 2.1\)  Jy at 1.7 GHz ([2]}. We show
the extrapolation of this up through our optical/UV/X-ray bandpass
assuming a flat spectrum (black line on Fig. REF a). This is a factor
\(\sim 3\)  below the observed optical flux, but this is the maximum
possible jet contribution as its spectrum should break where it
becomes optically thin. It seems most likely that this break is at IR
frequencies ([3]}; [4]}) so the jet is also
probably negligible in the optical/UV for these data. Thus X-ray
reprocessing from hard X-ray illumination of the outer disc seems the
most likely origin for the optical/UV flux [5]}.
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